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Re: [PATCH] x86-64: Implement strcpy family IFUNC selectors in C

From: "H.J. Lu" <hjl dot tools at gmail dot com>
To: Florian Weimer <fweimer at gapps dot redhat dot com>
Cc: GNU C Library <libc-alpha at sourceware dot org>
Date: Sun, 11 Jun 2017 12:46:24 -0700
Subject: Re: [PATCH] x86-64: Implement strcpy family IFUNC selectors in C
Authentication-results: sourceware.org; auth=none
References: <20170611135042.GA22931@gmail.com> <c9e0c022-5cd7-ca7c-6b4e-927b1629ee57@gapps.redhat.com>

On Sun, Jun 11, 2017 at 11:22 AM, Florian Weimer
<fweimer@gapps.redhat.com> wrote:
> On 06/11/2017 03:50 PM, H.J. Lu wrote:
>>
>> All internal calls within libc.so can use IFUNC on x86-64 since unlike
>> x86, x86-64 doesn't need to reserve a register to make a PLT call.
>
>
> Shouldn't this rather say, “because, unlike x86, x86-64 supports PC-relative
> addressing to access the GOT entry”?  That's probably the root cause of the

Both are true.  The end result is there is no extra needed for call
via PLT.

> performance difference.
>
> Thanks,
> Florian



-- 
H.J.

Follow-Ups:
- Re: [PATCH] x86-64: Implement strcpy family IFUNC selectors in C
  - From: H.J. Lu

References:
- [PATCH] x86-64: Implement strcpy family IFUNC selectors in C
  - From: H.J. Lu
- Re: [PATCH] x86-64: Implement strcpy family IFUNC selectors in C
  - From: Florian Weimer

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